Counterbalance means



Oct. II, 1966 J. CHASTAIN COUNTERBALANCE MEANS Original Filed Nov. 15,1961 D Joe Chosfoin Fig. 4 BY ATTORNEYS SYROK E, INCHES United StatesPatent M 3,277,730 COUNTERBALANCE MEANS Joe Chastain, P.O. Box 4035,Midland, Tex. Original application Nov. 13, 1961, Ser. No. 151,723, nowPatent No. 3,222,940, dated Dec. 14, 1965. Divided and this applicationJuly 20, 1965, Ser. No. 482,972 4 Claims. or. 74-41 This inventionrelates to counterbalance means for balancing unequal loads which aremoved in alternate reciprocal movements and, more particularly, tocounterbalance means for reducing the peak torques on the drive shaft ofa power unit which is adapted to move the unequal reciprocating loadsThis application is a division of my co-pending application, Serial No.151,723, filed November 13, 1961, now Patent No. 3,222,940, patentedDecember 14, 1965.

One object of this invention is to provide a new and improvedcounterbalance means for unequal reciprocating loads which are moved inreciprocation whereby the peaking of torque on the drive shaft of thepower unit moving such loads is reduced.

Another object of the invention is to provide a new and improvedcounterbalance means adapted for application to reciprocating movementpumps and to provide load equalizing means whereby the variations in theload on the motor driving the pump are minimized during each cycle ofoperation of the pump.

Still another object is to provide a new and improved pump, of thereciprocating movement type, having a counterbalance means whichautomatically varies in ac cordance with the reciprocating movement ofthe pull or lift rods of the pump to minimize the variations in the loadon the motor during each cycle of operation of the pump.

A further object is to provide a reciprocating movement type pumpincluding a pump jack and a mechanical linkage for translating therotary motion of a drive shaft to oscillating movement of the pump jacklever wherein the driving means directly connected to the pump jacklever for oscillating the same forms one side of a parallelogram linkagewhich maintains the angle between the driving means and pump jack leverat approximately ninety degrees and wherein the line of force applied toone end of the pump jack lever by said driving means is parallel to theline of force applied by the opposite end of said pump jack lever to thepull or lift rods of the pump throughout the upstroke and downstrokemovements of the pump jack lever, thereby effecting an efiicienttransfer of energy between the drive shaft and pump lift rods.

A still further object is to provide a new and improved counterbalancemeans adapted for application to reciprocating movement pumps whereinthe effective force of a counterbalance mass or weight is varied duringeach cycle of operation of the pump to provide for a uniformdistribution of torque on the drive shaft of the motor driving the pump.

A still further object is to provide a new and improved counterbalancemeans adapted for application to reciprocating movement pumps whichvaries automatically in accordance with the reciprocating movement ofthe pull or lift rods of the pump to minimize variations in the load onthe motor driving the pump and to provide for a uniform distribution oftorque on the motor drive shaft during a cycle of operation of the pumpwithout any pronounced peaking.

3,277,736 Patented Oct. 11, 1966 Additional objects and advantages ofthe invention will be readily apparent from the reading of the followingdescription of a device constructed in accordance with the invention,and reference to the accompanying drawings thereof, wherein:

FIGURE 1 is a schematic fragmentary side view of a pump mechanismincluding a pump jack and counterbalance means therefor and showing theparts thereof in the positions they assume during the downstroke of theP p;

FIGURE 2 is a schematic fragmentary side view of the mechanism of FIGURE1 showing the parts thereof in the positions they assume during theupstroke of the P p;

FIGURE 3 is a fragmentary end view of the pump mechanism of FIGURE 1;

FIGURE 4 is a graphic comparison of the load capacifor with a constantinput torque of a unit with the counterbalance means of this inventionand a unit with a conventional counterbalance means; and,

FIGURE 5 is a fragmentary side elevation of a modification of themechanism of FIGURE 1.

Referring now particularly to FIGURES 1 to 3 of the drawings, areciprocating movement pump jack mech anism 10 is shown mounted on aflat base or support 11. The pump, itself, may be of a type suitable forpumping wells, such as oil wells, whereby a piston (not shown) may beattached in the usual manner to the pull or lift rods 13 of the pump andslidably mounted in a well flow conductor or casing which communicateswith a pool or reservoir of liquid to be pumped. The piston may beprovided with a conventional by-pass valve or gasket which will permitflow of liquid in the conductor past the piston during the downwardstroke of the lift rods and piston and which will prevent flow of liquidpast the piston during the upstroke of the lift rods and piston, therebycausing the liquid to be lifted out of the reservoir during theupstrokes of the lift rods and piston.

The lift rods are attached to an arcuate support or horsehead 14 at theend of the pump jack lever or walking beam 15 from which they aresuspended substantially vertically. A bracket 17 attached to theunderside of the pump jack lever intermediate its ends is provided witha sleeve, saddle bearing or the like, for connection with a horizontallydisposed pivot bar or shaft 18 mounted in the upper ends of a supportframe 19. The support frame may include a substantially vertical Samsonpost 20 and an angular brace 20a. The pivot bar 18 thus provides afulcrum for the reciprocating oscillatory movements of the pump jacklever.

The end of the pump jack lever remote from the lift rods has a bracket21 attached to its underside providing a tail-bearing connection with ahorizontal pivot pin 21a which is connected at its ends to a pair ofpitman rods 22 by means of suitable bearing couplings 23. The pitmanrods extend downwardly parallel to each other and are pivotallyconnected at their lower ends to a drive crank or arms 24 by means ofpitman bearing couplings 25. Each of the couplings 25 receives ahorizontally disposed crank pin or pivot 27 carried by its associateddrive crank or arm at a point intermediate its ends. The drive cranksare mounted parallel to one another on opposite ends of a transmissiondriven shaft 28 of a speed reducer 29. The shaft 28 is driven by a driveshaft 30 of the speed reducer, being connected to the drive shaft by adrive chain 32, or other suitable means, such as a gear train, whichoperatively connects a driven sprocket 33 on the transmission drivenshaft with a drive sprocket 34 on the drive shaft. The drive shaft 30 isjournalled in a pair of upright bearing supports 35 and 36 on the base11. The gears and chain of the speed reducer 29 are enclosed within ahousing or gear box case 37 having at its lower end a hollow bearingsleeve (not shown) which is journalled on the drive shaft 30 so that thespeed reducer housing may pivot about the drive shaft. The drive shaft30 has a pulley 39 rigidly secured thereon so that the drive shaft maybe rotated by a suitable belt (not shown) driven by a motor (not shown),in the usual manner.

A pair of auxiliary beams or levers 40 .are each attached at one end toa coupling 40a rotatably disposed on the crank pins or pivots 27. At itsother end each auxiliary beam is pivotally connected to the Samson post20 by a pivot pin 41 mounted in a bearing bracket 42 secured to theSamson post preferably substantially vertically below the pivot bar 18for the pump jack lever. As shown in FIGURES 1 and 2, the auxiliarybeams 40 are disposed parallel with the walking beam or pump jack lever15. The pitman rods 22, which are parallel to one another, are alsodisposed substantially parallel to the plane between the fulcrum pivot18 and the pivots 4-1 on the Samson post 20 and to the pump lift rods13, thus describing a parallelogram linkage or framework wherein theauxiliary beams 40 constitute one side of the parallelogram and togetherwith the pump jack lever comprise a first pair of opposite sides, whilethe pitman rods 22 which are connected to the pump jack and auxiliarybeams also form one side of the linkage and are maintained substantiallyparallel to the plane through the pivots 118 and 41 at the other side ofthe linkage. It will also particularly be seen that the pitman rods 22are at all times maintained substantially parallel to the pump lift rods13 by virtue of their connection with the pump jack lever 15 and theauxiliary beams 40 of the parallelogram linkage which swing from thestationary support 19 to maintain the pitman rods in a vertical positionparallel to such lift rods during the swinging reciprocating movement ofthe pump jack lever. The lift rods 13 move in a vertical line because oftheir flexible connection with the horsehead 14.

It will thus be apparent that the cranks 24, which are drivensimultaneously in a rotary movement about the transmission shaft 28 ofthe speed reducer, cause the pitman rods 22 and the end of the pump jacklever 15 to which the pitman rods are secured to move downwardlyrelative to the shaft 28 as the cranks are moved downwardly in acounterclockwise direction as shown in FIG- URE 2. Further, it will beseen that the pitman rods and the end of the pump jack lever to whichthey are secured move upwardly relative to the shaft 28 as the cranksmove upwardly in a counterclockwise direction as shown in FIGURE 1.However, because of the provision of the auxiliary beams 40 which holdthe lower ends of the pitman rods, the gear box is forced to oscillatein a limited arc of pivotal movement about the shaft 30 as the cranksare rotated by the shaft 28. The speed reducer gear box is pivoted tothe right, as shown in FIG- URE 2, when the cranks move downwardly; andto the left, as shown in FIGURE 1, when the cranks move upwardly. Thearcuate distance of pivotal movement of the speed reducer gear box ispreferably substantially equal to the vertical stroke of the pumpingunit lift rods.

Like the pump jack lever :15, the auxiliary beams 40 which hold thelower ends of the pitmans are also subjected to a limited pivotalmovement about their respective pivots 41 by the rotation of the cranks.Thus, the pitmans are moved laterally toward and away from the Samsonposts during each cycle of rotation of the cranks, the amount of suchlateral movement being very small, since the arcs described by thepivoted ends of the pump jack lever and the auxiliary beams are small asl compared to the length of the lever arms forced thereby. Consequently,the pitman rods 22 remain substantially vertical at all times and theforce applied thereto is substantially longitudinal thereof at alltimes, and is parallel to the force applied on the horsehead end of thecrank jack by the load acting on the pump lift rods.

It will be apparent that the torque on the drive shaft or power shaftcaused by the weight of the lift rods and piston, and the column offluid supported on the piston, will change during each cycle ofoperation of the pump. The peak torque load during the upstroke of therods will have a large positive value because of the weight of the liftrods and the fluid supported on the piston, whereas during thedownstroke the weight of the lift rods and such fiuid as remains on thepiston will act to produce a negative torque on the shaft. Thus, it willbe noted that the greater the weight of the column of fluid lifted, thegreater will be the peak torque on the driving shaft during thedownstroke and upstroke in each cycle of operation of the pump, and thegreater will be the loads imposed on the speed reducer and the motor.

To reduce these torque peaks, a counterbalance weight W is mounted oneach crank arm 24 at the end thereof which is remote from the drivenshaft 28 of the speed reducer, the mass of the weights and the distancesfrom the driven shaft 28 when the same are secured to the crank armsdetermining the effective force exerted by such weights. It will benoted that during the upstroke or lifting movment of the pump 10, asillustrated in FIGURE 2, the crank 24 and counterweights W apply orexert a downward force on the pitman rods and therefore on the end ofthe walking beam of the pump jack which is remote from the lift rods.Thus, during the upstroke movement of the lift rods, the counterweightsW assist the power shaft of the prime mover in lifting the lift rods 13and the column of fluid above the piston. During the downstroke movementof the elements, as illustrated in FIGURE 1, it will be noted that thecounterweights W exert their force in opposition tothe swinging movementof the crank arm and resist upward movement of the pitman rods and theend of the pump jack remote from the lift rods. It will also be notedthat when the counterbalance weights W are positioned as shown in FIGURE2, during the upstroke of the pump jack, the counterweights act inconjunction with the force applied to the pitman rods by the crank armand thus produce a larger downward force acting on the pitman rods andon the pitman rod end of the pump jack lever to provide for theapplication of a greater lifting force to the lift rods 13. Thisarrangement therefore produces a greater effective downward forceapplied to the pitman end of the pump jack lever during the lifting orupstroke of the pump lift rods and a lesser or smaller effective forceon the pitman rod end of the pump lift rods, whereby the force appliedto the pitman rod end of the pump jack lever by the gear reducer, crankarms and counterweights varies in accordance with the load applied tothe horsehead end of the pump jack lever during the up and down strokesof the lift rods. It is believed obvious that the rotation of the crankarm may be in either direction, though it has been described ascounter-clockwise, and that rotation in either direction would producethe same effective force applied to the pitman rod end of the pump jacklever. The mass of the gear box always impose a slight torque actingdownwardly on the pitman rods except when it is in vertical alignmentwith such rods.

It is also to be noted that the pitmans 22 remain or are held in aposition substantially parallel to the lift rods 13 throughout therotary movement of the cranks and the pivotal movements of the pump jacklever and the auxiliary beams. Thus, the angle between the pitmans andthe pump jack lever changes but slightly throughout the up and downstrokes of the pump, and never varies greatly from ninety degrees.Consequently the force exerted on the pump jack lever approaches theefficiency obtainable with an ideal infinite length pitman. Of course,the counterbalance weights do not impose any torque on the pitman rods22 when the crank arm 24 is in vertical alignment with the pitmans 22.

It will also be seen that the torque or force applied to or imposed onthe pivots 27 at the lower end of the pitman rods and the outer end ofthe auxiliary beams by the gear reducer and counterweights during eachcycle of operation of the pump will always be opposite to the torque onsuch pivots resulting from the weight of the lift rods and piston andthe column of fluid supported on the pump piston. The graphicillustration in FIGURE 4 provides a comparison of the loads which can belifted by a conventional pumping unit with the loads which can be lifted'by a pumping unit having the parallelogram auxiliary beam constructionof this invention. In each case a constant torque is applied from thegear reducer 23 and a given counterbalance W is mounted on the crankarm. Curve A illustrates the maximum load capacity which can be liftedon the upstroke by the unit of this invention having the parallelogramauxiliary beam construction, and curve B illustrates the minimum loadcapacities which can be lifted on the downstroke of the same structure.The maximum load capacity which can be lifted by a conventional unit isillustrated in curve C showing the maximum load capacity for theupstroke of the unit. Curve D shows minimum load capacity for thedownstroke. If loads are greater on the upstroke or less on thedownstroke than the values indicated in the curves, then torque overloadwould result, with a torque applied to the gear reducer in excess of thecapacity of the gear reducer. It will particularly be noted that theload capacity available applied during the major portion of the movementof the crank arm and of the pump jack unit of this invention issubstantially level and gives space for a rectangular substantiallyhorizontal dynamometer card without overloading the pumping unit for theparallelogram structure of this invention, as compared with thenecessarily anguiarly disposed dynamometer card required for thestandard counterbalance structure.

It is readily apparent that, if desired, a counterbalance weight CW maybe applied to each of the auxiliary beams 40 of the form of theinvention described and illustrated in FIGURES 1 and 2. Such a modifiedstructure is shown in FIGURE 5, wherein the auxiliary beam 240 isprovided with an extension arm 24*1 extending in longitudinal alignmenttherewith beyond the connecting bearing 240a by means of which theauxiliary beam is connected to the pivot 27 of the crank arm 24 of theunit first described. Obviously, the counterbalance CW in thismodification of the invention is supplemented by the crank arm weight Win reducing the torque imposed on the transmission driven shaft 28 andthe drive shaft 30 by the load exerted on the horsehead end of the pumpjack lever during the upstroke of the pump lift rods.

It will thus be seen that the counterbalance means of both forms of theinvention described herein provide for a more uniform distribution oftorque without producing the pronounced peaking present in conventionalunits. In addition, no negative torque is imposed onthe drive shaft anda closer balance between maximum and minimum loads is effected.

It will further be seen that new and improved pump jack structures havebeen disclosed herein providing a parallelogram counterbalance meansminimizing variations in the load on the power unit or motor drive meansof the pump, reducing the torque peaks acting on the power unit andreducing the fluctuation of the torques acting on the unit.

The foregoing description of the invention is explanatory only, andchanges in the details of the construction illustrated may be made bythose skilled in the art, within the scope of the appended claims,without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A pump jack mechanism including: a support; a rotatable drive shaftcarried by said support; a power transmission unit mounted on said driveshaft and swingable in an are about said drive shaft; said transmissionunit having a driven shaft spaced from the drive shaft and driventhrough said power transmission unit by said drive shaft; a housing forsaid transmission unit supporting said driven shaft in spacedrelationship with respect to said drive shaft; a crank arm secured tosaid driven shaft and swingable about the axis of said driven shaftthrough a circular path and through an arcuate path with the housingabout the axis of the drive shaft; an elongate walking beam supportedintermediate its ends at a fixed point on said support for pivotalreciprocating movement about said fixed point on said support in asubstantially vertical plane, one end of said walking beam being adaptedto be connected to a reciprocably movable vertical load; a mechanicallinkage connecting said crank arm with one lever arm portion of saidwalking beam for effecting reciprocating movement of said walking beamupon rotation of said drive shaft; said linkage comprising an auxiliarybeam member pivotally mounted at one end on said support at a pointspaced substantially vertically below said fixed point for swingableoscillation in a substantially vertical plane about such pivotalconnection with said support; a connecting link member pivotallyconnected at one end to the end of the walking beam opposite saidreciprocably movable load and at its other end to said auxiliary beamadjacent its outer swingable end, said link member connecting saidelongate walking beam and said auxiliary beam parallel to each other,whereby said elongate walking beam is swingable about its pivotalmounting intermediate its ends by said auxiliary beam; connecting meansoperatively interconnecting the swingable end of said crank arm and saidauxiliary beam, whereby the swingable end of said crank arm is connectedwith said elongate swingable walking beam opposite the end of saidwalking beam to which said load is adapted to be connected for causingreciprocating oscillating movement of said walking beam upon rotarymovement of said crank arm by said drive shaft; and counterbalanceweight means on said crank arm outwardly of said crank arm from saiddrive shaft beyond the connection of said crank arm with said auxiliarybeam and swingable therewith for imposing a torque upon said linkage andsaid walking beam.

2. A pump jack mechanism of the character set forth in claim 1 andincluding: second counterbalance weight means mounted on said auxiliarybeam at a point spaced outwardly from the point of pivotal connection ofsaid crank arm with said auxiliary beam, said sec-0nd counterbalanceweight means coacting with said first counterbalance weight means on thecrank arm for varying the load applied to said walking beam.

3. A pump jack mechanism of the character set forth in claim 1 wherein:said counterbalance means connected with said crank arm is disposedoutwardly of said crank arm from the driven shaft beyond the point ofconnection of said crank arm with said auxiliary beam, whereby saidcounterbalance means imposes a weight load on said crank arm which ismovable between a point outwardly of said auxiliary beam beyond thepoint of connection of said connecting link member with said auxiliarybeam and a point in which said weight load is disposed inwardly of saidauxiliary beam between the point of connection of said connecting linkmember with said auxiliary beam and the pivotal mounting of saidauxiliary beam on said support for imposing a torque on said drive shaftor driven shaft which varies with the torque imposed on said drivenshaft by said reciprocably movable load.

4. A pump jack mechanism of the character set forth in claim 3 wherein:second counterbalance weight means is mounted on said auxiliary beam ata point spaced outwardly from the pivotal mounting of said auxiliarybeam 7 8 on said support beyond the connection of said beam with1,986,012 1/ 1935 Patterson 74-41 said connecting link member, saidsecond counterbalance 2 52 5 1 10 1959 Kelmer 74 41 X weight meanscoasting with said first counterbalance 2 579 112 12/1951 Fullerton 7111 Weight means of said crank arm for varying the load applied Walkmgbeam' 5 FRED c. MATTERN, 111., Primary Examiner.

References Cited by the Examiner BROUGHTON G. DURHAM, MILTON KAUFMAN,UNITED STATES PATENTS Examiners 1,592,391 7/1926 Stevenson 74-411,782,697 11/1930 Reschke 74 41 D. H. THIEL, Assistant Examiner.

1. A PUMP JACK MECHANISM INCLUDING: A SUPPORT; A ROTATABLE DRIVE SHAFTCARRIED BY SAID SUPPORT; A POWER TRANSMISSION UNIT MOUNTED ON SAID DRIVESHAFT AND SWINGABLE IN AN ARC ABOUT SAID DRIVE SHAFT; SAID TRANSMISSIONUNIT HAVING A DRIVEN SHAFT SPACED FROM THE DRIVE SHAFT AND DRIVENTHROUGH SAID POWER TRANSMISSION UNIT BY SAID DRIVE SHAFT; A HOUSING FORSAID TRANSMISSION UNIT SUPPORTING SAID DRIVEN SHAFT IN SPACEDRELATIONSHIP WITH RESPECT TO SAID DRIVE SHAFT; A CRANK ARM SECURED TOSAID DRIVEN SHAFT AND SWINGABLE ABOUT THE AXIS OF SAID DRIVEN SHAFTTHROUGH A CIRCULAR PATH AND THROUGH AN ARCUATE PATH WITH THE HOUSINGABOUT THE AXIS OF THE DRIVE SHAFT; AN ELONGATE WALKING BEAM SUPPORTEDINTERMEDIATE ITS ENDS AT A FIXED POINT ON SAID SUPPORT FOR PIVOTALRECIPROCATING MOVEMENT ABOUT SAID FIXED POINT ON SAID SUPPORT IN ASUBSTANTIALLY VERTICAL PLANE, ONE END OF SAID WALKING BEAM BEING ADAPTEDTO BE CONNECTED TO A RECIPROCABLY MOVABLE VERTICAL LOAD; A MECHANICALLINKAGE CONNECTING SAID CRANK ARM WITH ONE LEVER ARM PORTION OF SAIDWALKING BEAM FOR EFFECTING RECIPROCATING MOVEMENT OF SAID WALKING BEAMUPON ROTATION OF SAID DRIVE SHAFT; SAID LINKAGE COMPRISING AN AUXILIARYBEAM MEMBER PIVOTALLY MOUNTED AT ONE END ON SAID SUPPORT AT A POINTSPACED SUBSTANTIALLY VERTICALLY BELOW SAID FIXED POINT FOR SWINGABLEOSCILLATION IN A SUBSTANTIALLY VERTICAL PLANE ABOUT SUCH PIVOTALCONNECTION WITH SAID SUPPORT; A CONNECTING LINK MEMBER PIVOTALLYCONNECTED AT ONE END TO THE END OF THE WALKING BEAM OPPOSITE SAIDRECIPROCABLY MOVABLE LOAD AND AT ITS OTHER END TO SAID AUXILIARY BEAMADJACENT ITS OUTER SWINGABLE END, SAID LINK MEMBER CONNECTING SAIDELONGATE WALKING BEAM AND SAID AUXILIARY BEAM PARALLEL TO EACH OTHER,WHEREBY SAID ELONGATE WALKING BEAM IS SWINGABLE ABOUT ITS PIVOTALMOUNTING INTERMEDIATE ITS ENDS BY SAID AUXILIARY BEAM; CONNECTING MEANSOPERATIVELY INTERCONNECTING THE SWINGABLE END OF SAID CRANK ARM AND SAIDAUXILIARY BEAM, WHEREBY THE SWINGABLE END OF SAID CRANK ARM IS CONNECTEDWITH SAID ELONGATE SWINGABLE WALKING BEAM OPPOSITE THE END OF SAIDWALKING BEAM TO WHICH SAID LOAD IS ADAPTED TO BE CONNECTED FOR CAUSINGRECIPROCATING OSCILLATING MOVEMENT OF SAID WALKING BEAM UPON ROTARYMOVEMENT OF SAID CRANK ARM BY SAID DRIVE SHAFT; AND COUNTERBALANCEWEIGHT MEANS ON SAID CRANK ARM OUTWARDLY OF SAID CRANK ARM FROM SAIDDRIVE SHAFT BEYOND THE CONNECTION OF SAID CRANK ARM WITH SAID AUXILIARYBEAM AND SWINGABLE THEREWITH FOR IMPOSING A TORQUE UPON SAID LINKAGE ANDSAID WALKING BEAM.